A tyre curing mold is in the form of a hollow cylinder, and comprises two flat, circular, parallel, opposite sidewalls defining the top and bottom walls of the mold; and a number of lateral sectors arranged successively to define the cylindrical lateral wall of the mold.
To insert a green tyre inside the mold and remove the cured tyre from the mold, the lateral sectors are movable radially to and from an engaged position, in which the lateral sectors contact the sidewalls.
In actual use, a tyre curing mold is inserted inside a container designed to hold the component parts (lateral sectors and sidewalls) of the curing mold together during the curing operation, and to permit release of the component parts of the curing mold to insert a green tyre and remove the cured tyre. The container normally comprises a system of inclined surfaces activated by a press to move the lateral sectors radially with respect to the sidewalls. This solution is adopted in that it provides for gripping the lateral sectors against the sidewalls with sufficient force to counteract the pressure (normally at least 20 bars) produced inside the mold during the curing operation.
One example of a tyre curing mold and container is described in Patent Application WO2004009337A1.
A vacuum container for a curing mold has been proposed, in which, once the green tyre is inserted, the container is connected to a vacuum pump to produce a vacuum inside the container (and therefore inside the curing mold) to improve fill of the curing mold by the green tyre and prevent the formation of air pockets. One example of a vacuum container for a curing mold is described in Patent EP0701894B2.
The vacuum container in Patent EP0701894B2, however, has several drawbacks, by comprising two dynamic, i.e. sliding, annular seals (O-rings), which are subject to severe wear, caused by a combination of pressure and the sliding movement of the seals, and must therefore be changed frequently, thus resulting in high maintenance cost of the vacuum container.